Field of the Invention
The present invention relates, in general, to devices for conducting electrical signals between bodies undergoing relative rotational motion and, more specifically, to electrical slip rings.
Electrical slip rings are widely used to conduct electrical signals between a first stationary body and a second body undergoing rotation relative to the first body. A typical slip ring includes a stator and a rotor rotatably connected thereto. A number of brushes and contact rings are mounted on the stator and rotor and are disposed in continuous sliding contact, unless a brush lifter mechanism which separates the brushes from the contact rings is activated. One to several brushes may be in contact with each contact ring. Either the brushes or the contact rings may be mounted on the rotor; while the mating contact ring or brush is mounted on the stator.
Slip rings have been used to provide a connection path for a variety of sensors, such as strain gages, thermocouples, pressure transducers, resistance temperature devices (RTDs), torque transducers, accelerometers, velocity sensors, etc., mounted on a rotating member, such as a train axle or wheel, an automobile wheel, etc., to a data acquisition unit located on the train or vehicle remote from the sensors.
There is a particular need to measure dynamic torques in automobile drive shafts and similar applications. In a common approach, a slip ring assembly is mounted outboard of the front wheel of a front wheel drive vehicle. Wires from the strain gage pass through the universal joints which requires modification of the axle shafts. This requires modification of the axle shafts, and the slip rings are exposed and clearly visible.
There have also been attempts to produce tubular slip ring assemblies that surround axle shafts. However, such tubular slip ring assemblies have not proven to be reliable in use.
Thus, it would be desirable to provide a slip ring for use in a rotating electrical signal generating data acquisition apparatus which overcomes the aforementioned problems relating to the use and construction of slip rings. It would also be desirable to provide such an apparatus which has a small size for easy mounting on an existing rotatable member undergoing testing. Finally, it would be desirable to provide a reliable slip ring apparatus which can be mounted around a tubular insulating member.